Reinforced concrete roads conventionally comprise a foundation layer, the so-called sub-base, usually of un-reinforced concrete, and the pavement or so-called base slab, which is reinforced, and is poured directly onto the sub-base.
Typically, the base slab is reinforced by a rectangular grid of steel reinforcing rods comprising a plurality of spaced apart longitudinal rods extending in the direction of the road and a plurality of spaced apart transverse rods extending athwart the longitudinal rods and tied thereto at each crossing point in the mesh. The longitudinal rods are individually fairly short, say 12 metres long, but successive longitudinal rods are spliced together, that is to say, overlapped and tied to each other, to form a continuous ribbon of mesh extending along the road. That ribbon is supported from the sub-base by plastic or other bar chairs to ensure that the reinforcement is at the correct altitude in the finished pavement.
Hitherto, the mesh ribbon has been formed in-situ by a team of steel fixers by hand. This not only involves manhandling all the steel into place and tying the individual rods together while stooped over double, but also requires the preparatory steps of marking the edge of the pavement on the base-base with a chalk line and spot marking the location of the individual transverse rods with paint to ensure that the fixers install the reinforcement to specification. The work is laborious and time consuming. Typically a team of twelve workers can put the reinforcement in place for 200 to 250 meters of two lane pavement per day.
In Australian patent no. 752 385 issued in the name of the present inventor, the entire contents of which are herein incorporated by way of cross-reference, a mobile workstation is disclosed for assembling and laying of pavement reinforcing bars. The mobile workstation has a wheeled chassis adapted to travel a route along which the pavement is to be laid. The mobile workstation carries longitudinal guide and spacing means that is positioned to receive longitudinal reinforcing rods and to space the longitudinal reinforcing rods apart from each other in a transverse direction. The mobile workstation also includes an open topped magazine for holding a quantity of transverse reinforcing rods. In use, the longitudinal reinforcing rods are positioned in the longitudinal rod guide and spacing means and travel over the open-topped magazine. The transverse rods in the open topped magazine are connected one at a time to the longitudinal rods to form a reinforcing mesh. The reinforcing mesh then slides over an apron at the rear of the mobile workstation and the mesh is deposited behind the chassis as the chassis moves ahead.
The mobile workstation described in Australian patent no. 752 385 has resulted in increases in production of between 60% and 100% when compared with conventional methods for laying and typing pavement reinforcement.
Another recent development in laying and assembling reinforcement involves the use of BAMTEC technology. This technology connects a number of reinforcing bars together by welding each bar to flexible steel straps at desired spacing. The thus-connected bars are then rolled up into rolls. When it is time to install the reinforcement, the rolls of reinforcing bars are placed at an appropriate position and simply unrolled. Thus, installation is very quick. Moreover, the spacing and the thickness of the reinforcing rods can be determined for each application using appropriate design criteria and the reinforcing rolls utilising the required rod thickness and spacing can be pre-assembled at a factory for subsequent delivery to the site. BAMTEC is a registered trade marks of Bam AG.
Any discussion of documents, publications, acts, devices, substances, articles, materials or the like which is included in the present specification has been done so for the sole purpose so as to provide a contextual basis for the present invention. Any such discussions are not to be understood as admission of subject matter which forms the prior art base, or any part of the common general knowledge of the relevant technical field in relation to the technical field of the present invention to which it extended at the priority date or dates of the present invention.